To go mono in and stereo out, look at "Input and Output Modes" on p.22 of the User Manual. Or, hit LEVELS twice and look at I/O Mode.
Many of the effects are "summed in, stereo out," which comes down to the same thing. Look at the Algorithms Manual to see which these are.
ADAT in and ADAT out is covered in the User Manual (see "Digital Connections" on p.14 as a starting point). Needless to say, the signals are limited to stereo – the other ADAT tracks are passed through.
